Small-angle light scattering from spherulites

HS and SS domains can organize to form crystalline superstructures, especially in the case of solution cast samples. Spherulites with diameters from several thousands of nm up to about 20 //m were observed by small-angle light scattering (SALS) [167,168], and by using optical and electron microscopic methods [169-171]. 

Small-angle light scattering (SALS) is a suitable technique for determining the spherulitic radius, from four-lobe patterns [22,279-282] such as those shown in Figure 4.8. Equations such as the following can be used [280]... 

Crystallization of a semicrystalline block copolymer quenched from the melt will also be briefly reviewed. Chu and Hsiao [68] comprehensively reviewed recent developments in SAXS where they discussed simultaneous measurements with other techniques. Among recently developed techniques, we will focus on simultaneous SAXSAVAXS (wide-angle X-ray scattering) and/or Hv-SALS (depolarized small-angle light scattering) measurements [69,70] because these are powerful techniques to study crystallization and spherulitic higher-order hierarchical structures in semicrystalline block polymers [71,72]. Current developments will also be reviewed later in the subsection on semicrystalline block polymers. 

Optical microscopy can be used as a complementary techihque to small-angle light scattering for the determination of spherulite dimensions. However, in optical microscopy, when the diameter of the spherulites is substantially less than the thickness of the film it is difficult to distinguish between spherulites that overlap within the plane of the specimen. On the other hand, if a very thin section cut from a thicker sample is examined by optical microscopy, a relatively small proportion of the spherulites observed will contain the equatorial plane representative of the true spherulite dimensions. 

By means of several optical techniques, viz. small angle laser light scattering (SALLS), optical microscopy, etc, the spherulite structure can be studied. From the photographic scattering pattern the spherulitic radius, R, can be calculated as a function of the crystallization time and/or blend composition [Stein, 1964] ... 

Thus we can conclude that early stage crystallization is characterized by an increase in the magnitude of the limiting slope (from 2 to 4) while spherulite growth is characterized by a decrease (from 4 to 2.7). Our results demonstrate that small angle scattering (light and X-rays) can be used to probe the early... 

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